CN115916441A

CN115916441A - Cutting insert for rotary cutting tool and rotary cutting tool

Info

Publication number: CN115916441A
Application number: CN202080103177.8A
Authority: CN
Inventors: 松原弘树; 后藤祥惠; 伊藤江平; 南亩冬弥
Original assignee: Sumitomo Electric Hardmetal Corp
Current assignee: Sumitomo Electric Hardmetal Corp
Priority date: 2020-09-02
Filing date: 2020-09-02
Publication date: 2023-04-04
Also published as: US20220339718A1; EP4209297A4; JPWO2022049659A1; EP4209297A1; WO2022049659A1; JP6977228B1

Abstract

The cutting insert for a rotary cutting tool has a top surface, a bottom surface, and an outer peripheral surface. The ridge between the top surface and the peripheral surface forms a cutting edge. The cutting edge includes a1 st line segment, a2 nd line segment, a3 rd line segment, a 4 th line segment, a1 st curved portion, a2 nd curved portion, a3 rd curved portion, and a 4 th curved portion. The angle formed between a straight line along the 1 st line segment and a straight line along the 3 rd line segment is an acute angle. The angle formed between a straight line along the 2 nd line segment and a straight line along the 4 th line segment is an acute angle. The angle formed between the straight line along the 2 nd line segment and the straight line along the 3 rd line segment is an obtuse angle. The angle formed between the straight line along the 1 st line segment and the straight line along the 4 th line segment is an obtuse angle. The radius of curvature of each of the 3 rd and 4 th curved portions is greater than the radius of curvature of the 1 st curved portion and greater than the radius of curvature of the 2 nd curved portion. The distance between the top surface and the bottom surface is equal to or shorter than the distance between the cutting edge and the bottom surface in a direction perpendicular to the bottom surface.

Description

Cutting insert for rotary cutting tool and rotary cutting tool

Technical Field

The present invention relates to a cutting insert for a rotary cutting tool (a cutting insert for a rotary cutting tool) and a rotary cutting tool.

Background

Japanese patent laying-open No. 2008-178967 (patent document 1) discloses a drill having a1 st throwaway tip and a2 nd throwaway tip. The ratio of the cutting load of the center edge formed by the 1 st throwaway tip to the cutting load of the outer peripheral edge formed by the 2 nd throwaway tip is set to be in the range of a: B = 52: 48 to 55: 45.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open No. 2008-178967

Disclosure of Invention

The cutting insert for a rotary cutting tool according to the present invention includes a top surface, a bottom surface, and an outer peripheral surface. The bottom surface is opposite to the top surface. The peripheral surface is continuous with each of the top surface and the bottom surface. The ridge between the top surface and the peripheral surface forms a cutting edge. The cutting edge includes: a1 st line segment; a2 nd line segment opposite to the 1 st line segment; a3 rd line segment inclined with respect to each of the 1 st and 2 nd line segments; a 4 th line segment opposite to the 3 rd line segment; a1 st bend connecting a1 st line segment and a3 rd line segment; a2 nd bend connecting the 2 nd line segment and the 4 th line segment; a3 rd bent portion connecting the 2 nd line segment and the 3 rd line segment; and a 4 th bend connecting the 1 st line segment and the 4 th line segment. The angle formed between a straight line along the 1 st line segment and a straight line along the 3 rd line segment is an acute angle. The angle formed between the straight line along the 2 nd line segment and the straight line along the 4 th line segment is an acute angle. The angle formed between the straight line along the 2 nd line segment and the straight line along the 3 rd line segment is an obtuse angle. The angle formed between the straight line along the 1 st line segment and the straight line along the 4 th line segment is an obtuse angle. A radius of curvature of each of the 3 rd and 4 th curved portions is greater than a radius of curvature of the 1 st curved portion and greater than a radius of curvature of the 2 nd curved portion. The distance between the top surface and the bottom surface is equal to or shorter than the distance between the cutting edge and the bottom surface in a direction perpendicular to the bottom surface.

Drawings

Fig. 1 is a schematic perspective view showing the structure of a cutting insert for a rotary cutting tool according to embodiment 1.

Fig. 2 is a schematic plan view showing the structure of the cutting insert for a rotary cutting tool according to embodiment 1.

Fig. 3 is a schematic cross-sectional view taken along line III-III in fig. 2.

Fig. 4 is a schematic cross-sectional view taken along line IV-IV in fig. 2.

Fig. 5 is a schematic perspective view showing the structure of the cutting insert for a rotary cutting tool according to embodiment 2.

Fig. 6 is a schematic plan view showing the structure of the cutting insert for a rotary cutting tool according to embodiment 2.

Fig. 7 is a schematic cross-sectional view taken along line VII-VII in fig. 6.

Fig. 8 is a schematic cross-sectional view taken along line VIII-VIII in fig. 6.

Fig. 9 is a schematic perspective view showing the structure of the rotary cutting tool according to embodiment 3.

Fig. 10 is a schematic perspective view showing a state in which a workpiece is machined using a rotary cutting tool.

Fig. 11 is a schematic diagram showing the trajectory of the cutting tool provided in the center-side cutting tool placement groove and the trajectory of the cutting tool provided in the outer-peripheral-side cutting tool placement groove.

Fig. 12 is an enlarged schematic view of the region XII of fig. 11.

Fig. 13 is a schematic cross-sectional view showing a flow of chips in a case where a workpiece is cut using a conventional cutting tool.

Fig. 14 is a schematic cross-sectional view showing the flow of chips in the case of cutting a workpiece using the cutting tool of embodiment 2.

Fig. 15 is a schematic cross-sectional view showing the flow of chips in the case of cutting a workpiece using the cutting tool of embodiment 1.

Fig. 16 is a diagram showing the structure of the cutting tool of samples 1 to 7.

Fig. 17 is a photograph showing chips of the work cut by the cutting tools of samples 1 to 7.

Fig. 18 is a graph showing the cutting resistance of the cutting tools of samples 1 to 7.

Fig. 19 is a graph showing the depths of scratches on the side surfaces of the holes formed by the cutting blades of samples 1 to 7.

Detailed Description

[ problems to be solved by the invention ]

Chip discharge performance greatly varies depending on workpieces. For example, chips of carbon steel are relatively easy to cut. On the other hand, chips of highly viscous workpieces such as stainless steel are difficult to cut off compared to carbon steel. When stainless steel is machined using the drill described in patent document 1, it is difficult to efficiently discharge chips.

The invention aims to provide a cutting tool for a rotary cutting tool and the rotary cutting tool, which can improve the chip discharge performance.

[ Effect of the invention ]

According to the present invention, a cutting insert for a rotary cutting tool and a rotary cutting tool capable of improving chip discharge performance can be provided.

[ description of embodiments of the invention ]

First, embodiments of the present invention will be described.

(1) The cutting insert 100 for a rotary cutting tool according to the present invention includes a top surface 1, a bottom surface 2, and an outer peripheral surface 3. The bottom surface 2 is opposite to the top surface 1. The peripheral surface 3 is continuous with each of the top surface 1 and the bottom surface 2. The ridge between the top surface 1 and the peripheral surface 3 forms a cutting edge 6. The cutting edge 6 includes:

line segment

1, 10; a2 nd line segment 20 opposite the 1 st line segment 10; line 3 segment

30, which is inclined with respect to each of the 1 st line segment 10 and the 2 nd line segment 20; a 4 th line segment 40 opposite the 3 rd line segment 30; a1 st bend 51 connecting the 1 st line segment 10 and the 3 rd line segment 30; a2 nd bend 52 connecting the 2

nd

20 and 4 th 40 line segments; a3 rd bent portion 53 connecting the 2 nd line segment 20 and the 3 rd line segment 30; and a 4 th bend 54 connecting the 1 st line segment 10 and the 4 th line segment 40. The angle formed between a line along the 1 st line segment 10 and a line along the 3 rd line segment 30 is acute. The angle formed between a line along segment 2 20 and a line along segment 4 40 is acute. The angle formed between a straight line along the 2 nd line segment 20 and a straight line along the 3 rd line segment 30 is an obtuse angle. The angle formed between a line along the 1 st line segment 10 and a line along the 4 th line segment 40 is an obtuse angle. The radius of curvature of each of the 3 rd curved portion 53 and the 4 th curved portion 54 is larger than the radius of curvature of the 1 st curved portion 51 and larger than the radius of curvature of the 2 nd curved portion 52. The distance between the top surface 1 and the bottom surface 2 in a direction perpendicular to the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2 or shorter than the distance between the cutting edge 6 and the bottom surface 2.

(2) According to the cutting insert 100 for a rotary cutting tool of the above (1), the distance between the top surface 1 and the bottom surface 2 may be equal to the distance between the cutting edge 6 and the bottom surface 2 in the direction perpendicular to the bottom surface 2.

(3) According to the cutting insert 100 for a rotary cutting tool according to the above (1), the top surface 1 may have the flat portion 50 spaced apart from the cutting edge 6. In a direction perpendicular to the bottom surface 2, a flat portion 50 may be located between the cutting edge 6 and the bottom surface 2.

(4) According to the cutting insert 100 for a rotary cutting tool relating to any one of the above (1) to (3), the top surface 1 may include: a1 st land surface 11 continuous with the 1 st line segment 10; a2 nd land surface 21 continuous with the 2 nd line segment 20; a3 rd land surface 31 continuous with the 3 rd line segment 30; and a 4 th land surface 41 continuous with the 4 th line segment 40. Each of the width of the 3 rd land surface 31 in the direction perpendicular to the 3 rd line segment 30 and the width of the 4 th land surface 41 in the direction perpendicular to the 4 th line segment 40 may be greater than the width of the 1 st land surface 11 in the direction perpendicular to the 1 st line segment 10 and greater than the width of the 2 nd land surface 21 in the direction perpendicular to the 2 nd line segment 20.

(5) According to the cutting insert for a rotary cutting tool 100 relating to any one of the above (1) to (4), each of the radius of curvature of the 3 rd curved portion 53 and the radius of curvature of the 4 th curved portion 54 may be 2 times or more and 5 times or less the radius of curvature of the 1 st curved portion 51, and may be 2 times or more and 5 times or less the radius of curvature of the 2 nd curved portion 52.

(6) According to the cutting insert 100 for a rotary cutting tool according to the above (1), the distance between the top surface 1 and the bottom surface 2 may be equal to the distance between the cutting edge 6 and the bottom surface 2 in the direction perpendicular to the bottom surface 2. The top surface 1 may include: a1 st land surface 11 continuous with the 1 st line segment 10; a2 nd land surface 21 continuous with the 2 nd line segment 20; a3 rd land surface 31 continuous with the 3 rd line segment 30; and a 4 th land surface 41 contiguous with the 4 th line segment 40. Each of the width of the 3 rd land surface 31 in the direction perpendicular to the 3 rd line segment 30 and the width of the 4 th land surface 41 in the direction perpendicular to the 4 th line segment 40 may be greater than the width of the 1 st land surface 11 in the direction perpendicular to the 1 st line segment 10 and greater than the width of the 2 nd land surface 21 in the direction perpendicular to the 2 nd line segment 20. Each of the radius of curvature of the 3 rd curved portion 53 and the radius of curvature of the 4 th curved portion 54 may be 2 times or more and 5 times or less the radius of curvature of the 1 st curved portion 51, and may be 2 times or more and 5 times or less the radius of curvature of the 2 nd curved portion 52.

(7) According to the cutting insert 100 for a rotary cutting tool according to the above (1), the top surface 1 may have the flat portion 50 spaced apart from the cutting edge 6. The flat portion 50 may be located between the cutting edge 6 and the bottom surface 2 in a direction perpendicular to the bottom surface 2. The top surface 1 may include: a1 st land surface 11 continuous with the 1 st line segment 10; a2 nd land surface 21 continuous with the 2 nd line segment 20; a3 rd land surface 31 continuous with the 3 rd line segment 30; and a 4 th land surface 41 continuous with the 4 th line segment 40. Each of the width of the 3 rd land surface 31 in the direction perpendicular to the 3 rd line segment 30 and the width of the 4 th land surface 41 in the direction perpendicular to the 4 th line segment 40 may be greater than the width of the 1 st land surface 11 in the direction perpendicular to the 1 st line segment 10 and greater than the width of the 2 nd land surface 21 in the direction perpendicular to the 2 nd line segment 20. Each of the radius of curvature of the 3 rd curved part 53 and the radius of curvature of the 4 th curved part 54 may be 2 times or more and 5 times or less the radius of curvature of the 1 st curved part 51, and may be 2 times or more and 5 times or less the radius of curvature of the 2 nd curved part 52.

(8) The rotary cutting tool according to the present invention includes: the cutting insert 100 for a rotary cutting tool according to any one of (1) to (7) above; and a main body portion holding the cutting insert 100 for a rotary cutting tool.

[ details of embodiments of the present invention ]

Next, the details of embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same reference numerals denote the same or equivalent portions, and a repetitive description thereof will not be repeated.

(embodiment 1)

First, the structure of the cutting insert 100 for a rotary cutting tool according to embodiment 1 will be described.

Fig. 1 is a schematic perspective view showing the structure of a cutting insert 100 for a rotary cutting tool according to embodiment 1. As shown in fig. 1, a cutting insert 100 for a rotary cutting tool according to embodiment 1 mainly includes: top surface 1, bottom surface 2, outer peripheral surface 3, and inner peripheral surface 4. The bottom surface 2 is opposite to the top surface 1. The bottom surface 2 is, for example, a flat surface. The peripheral surface 3 is continuous with each of the top surface 1 and the bottom surface 2. The ridge between the top surface 1 and the peripheral surface 3 forms a cutting edge 6. The top surface 1 is for example a rake surface. The outer peripheral surface 3 is, for example, a flank surface. The inner peripheral surface 4 is continuous with each of the top surface 1 and the bottom surface 2. The inner circumferential surface 4 defines a through-hole 5. The through-hole 5 is opened at each of the top surface 1 and the bottom surface 2. The outer circumferential surface 3 surrounds the inner circumferential surface 4.

Fig. 2 is a schematic plan view showing the structure of the cutting insert 100 for a rotary cutting tool according to embodiment 1. As shown in fig. 2, the cutting edge 6 is substantially parallelogram-shaped when viewed in a direction perpendicular to the bottom surface 2. The cutting edge 6 has a1 st line segment 10, a2 nd line segment 20, a3 rd line segment 30, a 4 th line segment 40, a1 st bent portion 51, a2 nd bent portion 52, a3 rd bent portion 53, and a 4 th bent portion 54. Segment 2 is opposite segment 1, segment 10. Segment 2 20 and segment 1 are substantially parallel. The 3 rd segment 30 is slanted with respect to each of the 1 st segment 10 and the 2 nd segment 20. Segment 4 40 is opposite segment 3 from segment 30. The 4 th line segment 40 is inclined with respect to each of the 1 st line segment 10 and the 2 nd line segment 20. The 4 th line segment 40 and the 3 rd line segment 30 are substantially parallel. Each of the 1 st line segment 10, the 2 nd line segment 20, the 3 rd line segment 30, and the 4 th line segment 40 extends linearly. Each of the 1 st line segment 10 and the 2 nd line segment 20 is a portion serving as a center edge. Each of the 3 rd line segment 30 and the 4 th line segment 40 is a portion serving as a peripheral edge.

As shown in fig. 2, an angle (1 st angle θ 1) formed between a straight line (1 st straight line L1) along the 1 st line segment 10 and a straight line (3 rd straight line L3) along the 3 rd line segment 30 is an acute angle. Similarly, an angle (2 nd angle θ 2) formed between a straight line (2 nd straight line L2) along the 2 nd line segment 20 and a straight line (4 th straight line L4) along the 4 th line segment 40 is an acute angle. In other words, each of the 1 st and 2 nd angles θ 1 and θ 2 is greater than 0 ° and less than 90 °. The 1 st angle θ 1 and the 2 nd angle θ 2 are substantially the same. Each of the 1 st angle θ 1 and the 2 nd angle θ 2 is, for example, 75 ° or more and 85 ° or less.

As shown in fig. 2, an angle (3 rd angle θ 3) formed between a straight line (2 nd straight line L2) along the 2 nd line segment 20 and a straight line (3 rd straight line L3) along the 3 rd line segment 30 is an obtuse angle. Similarly, an angle (4 th angle θ 4) formed between a straight line (1 st straight line L1) along the 1 st line segment 10 and a straight line (4 th straight line L4) along the 4 th line segment 40 is an obtuse angle. In other words, each of the 3 rd angle θ 3 and the 4 th angle θ 4 is greater than 90 ° and less than 180 °. The 3 rd angle θ 3 and the 4 th angle θ 4 are substantially the same. Each of the 3 rd angle θ 3 and the 4 th angle θ 4 is, for example, 95 ° or more and 105 ° or less.

As shown in fig. 2, the 1 st bend 51 connects the 1 st line segment 10 and the 3 rd line segment 30. The 2 nd bend 52 connects the 2

nd

20 and 4 th 40 line segments. The 3 rd bend 53 connects the 2 nd line segment 20 and the 3 rd line segment 30. The 4 th bend 54 connects the 1 st line segment 10 and the 4 th line segment 40. Each of the 1 st bent portion 51, the 2 nd bent portion 52, the 3 rd bent portion 53, and the 4 th bent portion 54 is circular arc-shaped. The radius of curvature of the 1 st curved portion 51 (the 1 st radius of curvature R1) and the radius of curvature of the 2 nd curved portion 52 (the 2 nd radius of curvature R2) are substantially the same. The radius of curvature of the 3 rd curved portion 53 (the 3 rd radius of curvature R3) and the radius of curvature of the 4 th curved portion 54 (the 4 th radius of curvature R4) are substantially the same.

Each of the radius of curvature (the 3 rd radius of curvature R3) of the 3 rd curved portion 53 and the radius of curvature (the 4 th radius of curvature R4) of the 4 th curved portion 54 is larger than the radius of curvature (the 1 st radius of curvature R1) of the 1 st curved portion 51 and larger than the radius of curvature (the 2 nd radius of curvature R2) of the 2 nd curved portion 52. In other words, the 3 rd radius of curvature R3 is greater than each of the 1 st radius of curvature R1 and the 2 nd radius of curvature R2. The 4 th radius of curvature R4 is greater than each of the 1 st radius of curvature R1 and the 2 nd radius of curvature R2.

Each of the radius of curvature of the 3 rd curved portion 53 (the 3 rd radius of curvature R3) and the radius of curvature of the 4 th curved portion 54 (the 4 th radius of curvature R4) may be 2 times or more and 5 times or less the radius of curvature of the 1 st curved portion 51 (the 1 st radius of curvature R1), and may be 2 times or more and 5 times or less the radius of curvature of the 2 nd curved portion 52 (the 2 nd radius of curvature R2). In other words, the 3 rd radius of curvature R3 may be 2 times or more and 5 times or less of each of the 1 st radius of curvature R1 and the 2 nd radius of curvature R2. The 4 th radius of curvature R4 may be 2 times or more and 5 times or less of each of the 1 st radius of curvature R1 and the 2 nd radius of curvature R2.

The lower limit of each of the radius of curvature of the 3 rd curved portion 53 and the radius of curvature of the 4 th curved portion 54 is not particularly limited, but may be, for example, 2.5 times or more, or may be 3 times or more the radius of curvature of the 1 st curved portion 51 and the radius of curvature of the 2 nd curved portion 52. The upper limit of each of the radius of curvature of the 3 rd curved portion 53 and the radius of curvature of the 4 th curved portion 54 is not particularly limited, but may be, for example, 4.5 times or less, or 4 times or less, the radius of curvature of the 1 st curved portion 51 and the radius of curvature of the 2 nd curved portion 52.

As shown in fig. 2, the top surface 1 may include: the 1 st land surface 11, the 2 nd land surface 21, the 3 rd land surface 31, the 4 th land surface 41, the 1 st inclined surface 12, the 2 nd inclined surface 22, the 3 rd inclined surface 32, the 4 th inclined surface 42, and the flat portion 50. The 1 st land surface 11 is continuous with the 1 st line segment 10. The 2 nd land surface 21 is continuous with the 2 nd line segment 20. The 3 rd land surface 31 is contiguous with the 3 rd line segment 30. The 4 th land surface 41 is continuous with the 4 th line segment 40. The flat portion 50 is continuous with the inner peripheral surface 4. The flat portion 50 is a convex surface. The flat portion 50 is spaced from the cutting edge 6. As shown in fig. 2, the flat portion 50 surrounds the through-hole 5 when viewed in a direction perpendicular to the bottom surface 2. The cutting edge 6 surrounds the flat portion 50 when viewed in a direction perpendicular to the bottom surface 2.

The 1 st inclined surface 12 is located between the 1 st land surface 11 and the flat portion 50. The 1 st inclined surface 12 is continuous with each of the 1 st land surface 11 and the flat portion 50. The 2 nd inclined surface 22 is located between the 2 nd land surface 21 and the flat portion 50. The 2 nd inclined surface 22 is continuous with each of the 2 nd land surface 21 and the flat portion 50. The 3 rd inclined surface 32 is located between the 3 rd land surface 31 and the flat portion 50. The 3 rd inclined surface 32 is continuous with each of the 3 rd land surface 31 and the flat portion 50. The 4 th inclined face 42 is located between the 4 th land face 41 and the flat portion 50. The 4 th inclined face 42 is continuous with each of the 4 th land face 41 and the flat portion 50.

As shown in fig. 2, each of the width of the 3 rd land surface 31 in the direction perpendicular to the 3 rd line segment 30 (the 3 rd land width W3) and the width of the 4 th land surface 41 in the direction perpendicular to the 4 th line segment 40 (the 4 th land width W4) may be larger than the width of the 1 st land surface 11 in the direction perpendicular to the 1 st line segment 10 (the 1 st land width W1) and may be larger than the width of the 2 nd land surface 21 in the direction perpendicular to the 2 nd line segment 20 (the 2 nd land width W2). In other words, the 3 rd blade width W3 is larger than each of the 1 st blade width W1 and the 2 nd blade width W2. The 4 th blade width W4 is larger than each of the 1 st blade width W1 and the 2 nd blade width W2. The 1 st blade width W1 and the 2 nd blade width W2 are substantially the same. The 3 rd blade width W3 and the 4 th blade width W4 are substantially the same.

The lower limit of each of the 3 rd and 4 th blade widths W3 and W4 is not particularly limited, but may be, for example, 2 times or more or 3 times or more the 1 st and 2 nd blade widths W1 and W2. The upper limit of each of the 3 rd and 4 th blade widths W3 and W4 is not particularly limited, but may be, for example, 10 times or less or 8 times or less as large as each of the 1 st and 2 nd blade widths W1 and W2.

As shown in fig. 2, a distance between the 3 rd line segment 30 and the 4 th line segment 40 in a direction parallel to the 1 st line segment 10 (1 st distance D1) may be greater than a distance between the 1 st line segment 10 and the 2 nd line segment 20 in a direction parallel to the 3 rd line segment 30 (2 nd distance D2). The lower limit of the 1 st distance D1 is not particularly limited, but may be, for example, 1.05 times or more or 1.08 times or more the 2 nd distance D2. The upper limit of the 1 st distance D1 is not particularly limited, but may be, for example, 1.5 times or less or 1.3 times or less of the 2 nd distance D2.

Fig. 3 is a schematic cross-sectional view taken along line III-III in fig. 2. The cross-section shown in fig. 3 is perpendicular to line 1, line 10 and to the bottom surface 2. In a direction perpendicular to the bottom surface 2, a distance between each of the 1 st land surface 11 and the 2 nd land surface 21 and the bottom surface 2 is equal to a distance between the cutting edge 6 and the bottom surface 2. From another point of view, each of the 1 st land surface 11 and the 2 nd land surface 21 is located on an imaginary plane including the 1 st line segment 10 and the 2 nd line segment 20. Each of the 1 st land surface 11 and the 2 nd land surface 21 is, for example, parallel to the bottom surface 2. The flat portion 50 is, for example, parallel to the bottom surface 2. Each of the 1 st land surface 11 and the 2 nd land surface 21 is, for example, parallel to the flat portion 50.

The 1 st inclined surface 12 is located between the 1 st land surface 11 and the flat portion 50 in a direction perpendicular to the bottom surface 2. The 1 st inclined surface 12 is inclined with respect to each of the 1 st land surface 11 and the flat portion 50. The 1 st inclined surface 12 is inclined toward the bottom surface side with respect to the 1 st land surface 11. The 2 nd inclined surface 22 is located between the 2 nd land surface 21 and the flat portion 50 in a direction perpendicular to the bottom surface 2. The 2 nd inclined surface 22 is inclined with respect to each of the 2 nd land surface 21 and the flat portion 50. The 2 nd inclined surface 22 is inclined toward the bottom surface side with respect to the 2 nd land surface 21.

The flat portion 50 is located between the cutting edge 6 and the bottom surface 2 in a direction perpendicular to the bottom surface 2. Specifically, the flat portion 50 is located between each of the 1 st and 2 nd land surfaces 11 and 21 and the bottom surface 2 in a direction perpendicular to the bottom surface 2. More specifically, the flat portion 50 is located between each of the 1 st inclined surface 12 and the 2 nd inclined surface 22 and the inner peripheral surface 4 in a direction perpendicular to the bottom surface 2.

Fig. 4 is a schematic cross-sectional view taken along line IV-IV in fig. 2. The cross-section shown in fig. 4 is perpendicular to line 3 and to the

bottom surface

2, 30. In a direction perpendicular to the bottom surface 2, a distance between each of the 3 rd and 4 th land surfaces 31 and 41 and the bottom surface 2 is equal to a distance between the cutting edge 6 and the bottom surface 2. From another point of view, each of the 3 rd land surface 31 and the 4 th land surface 41 is located on an imaginary plane including the 3 rd line segment 30 and the 4 th line segment 40. Each of the 3 rd and 4 th land surfaces 31 and 41 is, for example, parallel to the bottom surface 2. Each of the 3 rd and 4 th land surfaces 31 and 41 is, for example, parallel to the flat portion 50.

The 3 rd inclined surface 32 is located between the 3 rd land surface 31 and the flat portion 50 in a direction perpendicular to the bottom surface 2. The 3 rd inclined face 32 is inclined with respect to each of the 3 rd land face 31 and the flat portion 50. The 3 rd inclined surface 32 is inclined toward the bottom surface side with respect to the 3 rd land surface 31. The 4 th inclined surface 42 is located between the 4 th land surface 41 and the flat portion 50 in a direction perpendicular to the bottom surface 2. The 4 th inclined face 42 is inclined with respect to each of the 4 th land face 41 and the flat portion 50. The 4 th inclined surface 42 is inclined toward the bottom surface side with respect to the 4 th land surface 41.

The flat portion 50 is located between each of the 3 rd and 4 th land surfaces 31 and 41 and the bottom surface 2 in a direction perpendicular to the bottom surface 2. More specifically, the flat portion 50 is located between each of the 3 rd and 4 th inclined

surfaces

32 and 42 and the inner peripheral surface 4 in a direction perpendicular to the bottom surface 2. As shown in fig. 4, the distance between the outer peripheral surfaces 3 in the direction parallel to the bottom surface 2 may monotonically decrease from the top surface 1 toward the bottom surface 2.

As shown in fig. 3 and 4, in the direction perpendicular to the bottom surface 2, the distance between the top surface 1 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2, or the distance between the top surface 1 and the bottom surface 2 is shorter than the distance between the cutting edge 6 and the bottom surface 2. From another point of view, the top surface 1 is not located above the cutting edge 6 in a direction perpendicular to the bottom surface 2. Further from another point of view, the top surface 1 does not have a bulging-shaped curved surface portion (chip breaker) located above the cutting edge 6, and it is noted that a direction from the bottom surface 2 toward the top surface 1 corresponds to an upward direction.

(embodiment 2)

Next, the structure of the cutting insert 100 for a rotary cutting tool according to embodiment 2 will be described below. The cutting tool 100 for a rotary cutting tool according to embodiment 2 has the same configuration as the cutting tool 100 for a rotary cutting tool of embodiment 1, except mainly that the distance between the top surface 1 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2. Next, a description will be given mainly of a configuration different from that of the cutting insert 100 according to embodiment 1.

Fig. 5 is a schematic perspective view showing the structure of the cutting insert 100 for a rotary cutting tool according to embodiment 2. As shown in fig. 5, the top surface 1 of the cutting insert for a rotary cutting tool 100 according to embodiment 2 is a flat surface.

Fig. 6 is a schematic plan view showing the structure of the cutting insert 100 for a rotary cutting tool according to embodiment 2. As shown in fig. 6, the top surface 1 is substantially parallelogram-shaped when viewed in a direction perpendicular to the bottom surface 2. The top surface 1 surrounds the through hole 5. The top surface 1 is surrounded by a1 st line segment 10, a2 nd line segment 20, a3 rd line segment 30, a 4 th line segment 40, a1 st bend 51, a2 nd bend 52, a3 rd bend 53, and a 4 th bend 54.

Fig. 7 is a schematic cross-sectional view taken along line VII-VII in fig. 6. The cross-section shown in fig. 7 is perpendicular to the 1 st line segment 10 and also to the bottom surface 2. In a direction perpendicular to the bottom surface 2, the distance between the top surface 1 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2. From another perspective, the top surface 1 lies on an imaginary plane that includes the 1 st line segment 10 and the 2 nd line segment 20. The top surface 1 is for example parallel to the bottom surface 2.

Fig. 8 is a schematic cross-sectional view taken along line VIII-VIII in fig. 6. The cross-section shown in fig. 8 is perpendicular to

line

3, 30 and also to the bottom surface 2. In a direction perpendicular to the bottom surface 2, the top surface 1 is located on an imaginary plane including a3 rd line segment 30 and a 4 th line segment 40.

As shown in fig. 7 and 8, each of the width of the 3 rd land 31 in the direction perpendicular to the 3 rd line segment 30 (the 3 rd land width W13) and the width of the 4 th land 41 in the direction perpendicular to the 4 th line segment 40 (the 4 th land width W14) may be larger than the width of the 1 st land 11 in the direction perpendicular to the 1 st line segment 10 (the 1 st land width W11), and may be larger than the width of the 2 nd land 21 in the direction perpendicular to the 2 nd line segment 20 (the 2 nd land width W12). In other words, the 3 rd blade width W13 is larger than each of the 1 st blade width W11 and the 2 nd blade width W12. The 4 th blade width W14 is larger than each of the 1 st blade width W11 and the 2 nd blade width W12. The 1 st blade width W11 and the 2 nd blade width W12 are substantially the same. The 3 rd blade width W13 and the 4 th blade width W14 are substantially the same.

(embodiment 3)

Next, the structure of the rotary cutting tool according to embodiment 3 will be described.

Fig. 9 is a schematic perspective view showing the structure of the rotary cutting tool according to embodiment 3. As shown in fig. 9, the rotary cutting tool 200 according to embodiment 3 includes a main body 60 and a cutting insert 100 for rotary cutting tool. The rotary cutting tool 200 rotates about the rotation axis B. The body portion 60 holds the cutting insert 100 for a rotary cutting tool. The cutting insert 100 for a rotary cutting tool is, for example, the cutting insert 100 according to embodiment 1 or embodiment 2.

The body portion 60 has a front end face 61, a rear end face 65, an outer peripheral side face 62, and a fitting portion 64. The front end surface 61 is a portion opposed to the workpiece. The rear end face 65 is opposite to the front end face 61. The fitting portion 64 is continuous with the rear end surface 65. The fitting portion 64 is attached to a machine tool.

The main body 60 is formed with an outer peripheral side cutting tool receiving groove 71, a center side cutting tool receiving groove 72, and a chip discharge groove 63. The outer peripheral side cutting tool seating groove 71 is continuous with each of the outer peripheral side face 62 and the leading end face 61. The center-side cutting tool seating groove 72 is contiguous with the front end face 61 and spaced apart from the peripheral side face 62. The chip discharge groove 63 is spiral. The chip discharge groove 63 is provided around the rotation axis B.

In the rotary cutting tool 200, two cutting inserts 100 are attached to one main body portion 60. Specifically, one cutting tool 100 is mounted to the outer peripheral side cutting tool placing groove 71, and the other cutting tool 100 is mounted to the center side cutting tool placing groove 72. In the outer peripheral side cutting tool placing groove 71, the cutting tool 100 is arranged in such a manner that the 4 th line segment 40 (outer peripheral edge) is located axially forward. In the center-side cutting tool placement groove 72, the cutting tool 100 is arranged such that the 2 nd line segment 20 (center edge) is located axially forward. The mounting screw 73 is disposed in the through hole 5 of the cutting tool 100. The cutting insert 100 is attached to the body portion 60 using attachment screws 73. The bottom surface 2 of the cutting insert 100 is in contact with the body portion 60.

Fig. 10 is a schematic perspective view showing a state in which a workpiece is machined using the rotary cutting tool 200. As shown in fig. 10, a rotary cutting tool 200 is used to form a hole 83 in a workpiece 80. The bottom surface of the hole 83 has a center edge cutting region 81 and a peripheral edge cutting region 82. The central edge cutting region 81 is surrounded by the peripheral edge cutting region 82. The center-edge cutting region 81 is a region cut by the center edge of the cutting insert 100 provided in the center-side cutting insert placement groove 72. The outer peripheral edge cutting region 82 is a region cut by the outer peripheral edge of the cutting insert 100 provided in the outer peripheral side cutting insert placement groove 71.

Fig. 11 is a schematic diagram showing the trajectory of the cutting tool 100 disposed in the center-side cutting tool placement groove 72 and the trajectory of the cutting tool 100 disposed in the outer-periphery-side cutting tool placement groove 71. As shown in fig. 11, in the case of machining the workpiece 80 using the rotary cutting tool 200, the locus of the cutting tool 100 provided in the center side cutting tool placement groove 72 and the locus of the cutting tool 100 provided in the outer peripheral side cutting tool placement groove 71 are respectively symmetrical with respect to the rotation axis B. As shown in fig. 11, when viewed in the direction perpendicular to the rotation axis B, the locus of the cutting edge 6 of the cutting tool 100 provided in the center-side cutting tool placement groove 72 intersects the locus of the cutting edge 6 of the cutting tool 100 provided in the outer-peripheral-side cutting tool placement groove 71.

As shown in fig. 11, on the right side (on one side) of the rotation axis B as viewed in the direction perpendicular to the rotation axis B, the locus of the cutting edge 6 (center edge) of the cutting tool 100 provided in the center-side cutting tool placement groove 72 and the locus of the cutting edge 6 (outer peripheral edge) of the cutting tool 100 provided in the outer peripheral-side cutting tool placement groove 71 intersect with each other at the 1 st intersection point 91. The locus of the cutting edge 6 (center edge) of the cutting insert 100 provided in the center side cutting insert placement groove 72 and the locus of the cutting edge 6 (outer circumferential edge) of the cutting insert 100 provided in the outer circumferential side cutting insert placement groove 71 intersect each other at the 2 nd intersection point 92 on the left side (on the other side) of the rotation axis B as viewed in the direction perpendicular to the rotation axis B. In the radial direction perpendicular to the rotation axis B, the distance between the 1 st intersection 91 and the 2 nd intersection 92 corresponds to the center blade share amount A2.

As shown in fig. 11, on the right side (on one side) of the rotation axis B as viewed in the direction perpendicular to the rotation axis B, the 1 st outer peripheral point 93 is located on the outermost periphery of the trajectory of the cutting edge 6 (outer peripheral edge) of the cutting tool 100 provided in the outer peripheral side cutting tool placement groove 71. The 2 nd outer peripheral point 94 is located on the outermost periphery of the trajectory of the cutting edge 6 (outer peripheral edge) of the cutting insert 100 provided in the outer peripheral side cutting insert placement groove 71 on the left side (on the other side) of the rotation axis B as viewed in the direction perpendicular to the rotation axis B. In a radial direction perpendicular to the rotation axis B, a distance between the 1 st outer circumferential point 93 and the 2 nd outer circumferential point 94 is the tool diameter A1. The tool diameter A1 corresponds to the diameter of the hole 83 formed in the workpiece. The value obtained by subtracting the central edge separation amount A2 from the tool diameter A1 is the peripheral edge separation amount.

Fig. 12 is an enlarged schematic view showing a region XII in fig. 11. In fig. 12, the shape shown by the two-dot chain line indicates an imaginary corner of the cutting edge 6 in the case where the curvature radius of the 3 rd bent portion 53 is substantially zero. In this case, the 1 st intersection 91 is located at the imaginary intersection 95. As shown in fig. 12, the radius of curvature of the 3 rd bent portion 53 is increased so that the 1 st intersection 91 is offset toward the center by a distance A3. As a result, the center blade share amount A2 can be reduced. The centrifugal force applied to the chips cut by the central edge is smaller than the centrifugal force applied to the chips cut by the peripheral edges. Therefore, the chips cut by the central edge are more difficult to cut than the chips cut by the peripheral edges. As shown in fig. 12, the cutting balance is adjusted by increasing the radius of curvature of each of the 3 rd curved portion 53 and the 4 th curved portion 54 to decrease the center edge share amount A2.

The value obtained by dividing the center edge share amount A2 by the tool diameter A1 is the center edge share ratio. The center blade sharing rate is, for example, 48% to 53%. The upper limit of the center blade sharing rate is not particularly limited, but may be 52.5% or less, or 52% or less, for example. The lower limit of the center blade sharing rate is not particularly limited, but may be, for example, 48.5% or more, or 49% or more.

Next, the operational effects of the cutting insert 100 for a rotary cutting tool and the rotary cutting tool 200 according to the above-described embodiments will be described.

Fig. 13 is a schematic cross-sectional view showing the flow of chips 84 in the case of cutting a workpiece 80 using a conventional cutting tool 100. As shown in fig. 13, the conventional cutting tool 100 is provided with a mound-like chip breaker 7 arranged at a position higher than the cutting edge 6. Chips 84 of the workpiece 80 cut by the cutting edge 6 pass through the rake face and are then chipped by the chip breaker 7. For example, in the case of cutting a highly viscous workpiece 80 such as stainless steel, the chips 84 are chipped without being cut by the chip breaker. As a result, the chips 84 cannot be discharged efficiently.

Fig. 14 is a schematic cross-sectional view showing the flow of chips 84 in the case of cutting a workpiece 80 using the cutting tool 100 of embodiment 2. As shown in fig. 14, the top surface 1 and the cutting edge 6 of the cutting insert 100 according to embodiment 2 are located at the same height. Therefore, even in the case of cutting a highly viscous workpiece 80 such as stainless steel, the chips 84 of the workpiece 80 cut by the cutting edge 6 flow smoothly on the top surface 1. Therefore, the chips 84 can be suppressed from being chipped. As a result, the chips 84 can be efficiently discharged. In other words, the present inventors converted the existing concept of cutting the chips 84 into a concept of smoothly flowing the chips 84 and then rounding and discharging the chips in the chip discharge groove 63 of the main body portion 60. This can improve the discharge performance of the chips 84.

Fig. 15 is a schematic cross-sectional view showing the flow of chips 84 in the case of cutting a workpiece 80 using the cutting tool 100 of embodiment 1. As shown in fig. 15, the top surface 1 of the cutting insert 100 according to embodiment 1 is located at the same height as the cutting edge 6 or at a position closer to the bottom surface side than the cutting edge 6. Therefore, even in the case of cutting a highly viscous workpiece 80 such as stainless steel, the chips 84 of the workpiece 80 cut by the cutting edge 6 can flow smoothly on the top surface 1. This can suppress the chipping of the chips 84. The top face 1 further includes a1 st land face 11 and a1 st inclined face 12 continuing to the 1 st land face 11 and inclined toward the bottom face side with respect to the 1 st land face 11. Therefore, the contact area (wiping area) of the chip 84 with the top surface 1 can be reduced as compared with the cutting insert 100 of embodiment 2. This can reduce cutting resistance. As a result, the chips 84 can be discharged more efficiently.

In other words, according to the cutting insert 100 for a rotary cutting tool of the above-described embodiment, the distance between the top surface 1 and the bottom surface 2 is equal to the distance between the cutting edge 6 and the bottom surface 2, or the distance between the top surface 1 and the bottom surface 2 is shorter than the distance between the cutting edge 6 and the bottom surface 2 in the direction perpendicular to the bottom surface 2. Therefore, even in the case of cutting a highly viscous workpiece 80 such as stainless steel, the chips 84 of the workpiece 80 cut by the cutting edge 6 can flow smoothly on the top surface 1. This can suppress the chipping of the chips 84. As a result, the chip discharge performance can be improved.

In addition, each of the radius of curvature of the 3 rd curved portion 53 and the radius of curvature of the 4 th curved portion 54 is larger than the radius of curvature of the 1 st curved portion 51 and larger than the radius of curvature of the 2 nd curved portion 52. Thus, when the diameter of the rotary cutting tool 200 is changed, the center edge share amount A2 can be easily adjusted to fall within a desired range.

Further, according to the cutting insert 100 for a rotary cutting tool according to the above-described embodiment, each of the width of the 3 rd land surface 31 in the direction perpendicular to the 3 rd line segment 30 and the width of the 4 th land surface 41 in the direction perpendicular to the 4 th line segment 40 may be larger than each of the width of the 1 st land surface 11 in the direction perpendicular to the 1 st line segment 10 and the width of the 2 nd land surface 21 in the direction perpendicular to the 2 nd line segment 20. Each of the 3 rd line segment 30 and the 4 th line segment 40 corresponds to a peripheral edge. Each of the 1 st line segment 10 and the 2 nd line segment 20 corresponds to a center edge.

In order to improve the chip discharge performance, it is desirable that the chip 84 have a linearly extending shape. After the chip 84 is scraped on the land surface, the chip 84 takes a linearly extending shape. The greater the width of the land surface, the more likely the chip 84 becomes linearly extended. On the other hand, if the land surface has a large width, the distance over which the chips 84 are scraped on the land surface becomes long, and therefore the cutting resistance becomes large. In order to suppress an increase in cutting resistance, it is desirable that the width of the land face is small.

Since the peripheral edge is located on the outer peripheral side of the rotation axis B, the centrifugal force applied to the chip 84 cut by the peripheral edge is large. In this case, the force with which the chips 84 dig into the inclined surfaces (the 3 rd inclined surface 32 and the 4 th inclined surface 42) becomes large. Therefore, in order to make the chips 84 cut by the outer peripheral edge have a linearly extending shape, it is necessary to increase the width of the land surfaces (the 3 rd land surface 31 and the 4 th land surface 41) to some extent. On the other hand, since the center edge is located on the center side of the rotation axis B, the centrifugal force applied to the chip 84 cut by the center edge is small. In this case, the force with which the chip 84 drills into the rake faces (the 1 st rake face 12 and the 2 nd rake face 22) is small. Therefore, the width of the land surface (the 1 st land surface 11 and the 2 nd land surface 21) does not need to be so large in order to make the chip 84 cut by the center edge have a linearly extending shape.

The width of the land surface on the peripheral edge side is greater than the width of the land surface on the central edge side. Thereby, in each of the peripheral edge and the center edge, the chip 84 can be formed into a linearly extending shape while suppressing an increase in cutting resistance.

Further, according to the rotary cutting tool cutting insert 100 according to the above-described embodiment, each of the radius of curvature of the 3 rd curved portion 53 and the radius of curvature of the 4 th curved portion 54 may be 2 times or more and 5 times or less the radius of curvature of the 1 st curved portion 51, and may be 2 times or more and 5 times or less the radius of curvature of the 2 nd curved portion 52. Thus, in the rotary cutting tool 200 having the practical tool diameter A1, the central edge share amount A2 and the outer peripheral edge share amount can be set to the same level. Thereby, cutting resistance can be reduced when cutting a highly viscous work piece 80 such as stainless steel. Further, the depth of the scratch formed on the side surface of the hole 83 of the workpiece 80 can be reduced.

< example >

(preparation of sample)

Next, the cutting test will be described. In the cutting test, each of samples 1 to 7 was used as the cutting tool 100.

Fig. 16 is a diagram showing the structure of the cutting tool 100 of samples 1 to 7. As shown in fig. 16, in the cutting inserts 100 of samples 1 to 7, the curvature radii of the acute-angle-side curved portions (the 1 st curvature radius R1 and the 2 nd curvature radius R2) were all set to 0.6mm. In the cutting tools 100 of samples 1 to 7, the radii of curvature of the obtuse-angle-side curved portions (the 3 rd radius of curvature R3 and the 4 th radius of curvature R4) were set to 0.6mm, 1.0mm, 1.4mm, 1.8mm, 2.2mm, and 1.4mm, respectively.

In the cutting inserts 100 of samples 1 to 7, the ratios of the radius of curvature of the obtuse-angle-side curved portion to the radius of curvature of the acute-angle-side curved portion were 1, 1.67, 2.33, 3, 3.67, and 2.33, respectively. In the cutting tool 100 of samples 1 to 7, the center edge sharing rates were set to 52.9%, 52.0%, 50.7%, 50.1%, 48.9%, and 50.7%, respectively. The top surface 1 of the cutting insert 100 of sample 1 had a chip-breaker 7 (see fig. 13) in the shape of a bulge. The shape of the top surface 1 of each cutting tool 100 of samples 2 to 6 was set to a flat shape (see fig. 14). The shape of the top surface 1 of the cutting insert 100 of sample 7 was set to a concave shape (see fig. 15).

(cutting test conditions)

In the cutting test, the hole 83 was formed in each of the workpieces 80 using the rotary cutting tool 200 having the cutting tool 100 of sample 1 to sample 7. The machine tool used in the test was M/C BT50. The workpiece 80 used in the test was SUS316L. The drill diameter (Dc) was set to 20mm. The cutting speed (Vc) was set at 150m/min. The feed rate (f) was set to 0.08 mm/revolution. The depth (L) of each hole was set to 60mm. And processing by adopting a wet processing method (2 MPa).

(results of cutting test)

< shape of chip 84 >

Fig. 17 is a photograph showing chips of the workpiece 80 cut by the cutting tool 100 of samples 1 to 7. In fig. 17, each of the photographs on the upper side shows the entire chip, and each of the photographs on the lower side shows the chip in an enlarged manner. In fig. 17, longer chips are obtained by cutting with the center edge, and shorter chips are obtained by cutting with the peripheral edge. As shown in fig. 17, the chips of the workpiece 80 cut by the cutting tool 100 of sample 1 were greatly distorted and chipped. Therefore, a part of the chips of the workpiece 80 cut by the cutting tool 100 of sample 1 is caught in the chip discharge groove 63 and cannot be smoothly discharged. On the other hand, the chips of the workpiece 80 cut by the cutting tool 100 of each of samples 2 to 7 were substantially cylindrical and not greatly distorted. Therefore, the chips of the workpiece 80 cut by the cutting tool 100 of samples 2 to 7 are smoothly discharged through the chip discharge groove 63. From this, it was confirmed that the cutting insert 100 of each of the

embodiments

1 and 2 can improve the chip discharge performance of stainless steel.

< cutting resistance >

Fig. 18 is a graph showing the cutting resistance of the cutting insert 100 of each of the samples 1 to 7. In fig. 18, Z is the maximum value of the cutting resistance in the direction along the rotation axis B. X is the maximum value of the cutting resistance in the direction perpendicular to Z. Y is the maximum value of the cutting resistance in the direction perpendicular to each of X and Z. The maximum value of the cutting resistance in the Z direction of the cutting insert 100 of sample 2 is greater than that of the cutting insert 100 of sample 1. The maximum value of the cutting resistance of the cutting insert 100 of sample 2 in each of the X direction and the Y direction is smaller than the maximum value of the cutting resistance of the cutting insert 100 of sample 1 in each of the X direction and the Y direction.

In the case of the cutting insert 100 of sample 7, the maximum value of the cutting resistance in the Z direction was the smallest. Thus, it was confirmed that the cutting insert 100 according to embodiment 1 can reduce the cutting resistance in the Z direction. Among the cutting tools 100 of samples 2 to 6, the cutting tool 100 of sample 6 has the smallest cutting resistance in the Z direction. Thus, it was confirmed that the cutting resistance in the Z direction can be reduced by reducing the center edge sharing rate.

< depth of scratch on side surface of hole >

After the hole 83 is formed in the workpiece 80, the depth of the scratch formed on the side surface of the hole 83 is measured. Fig. 19 is a graph showing the scratch depths of the side surfaces of the holes 83 formed by the cutting inserts 100 of samples 1 to 7. As shown in fig. 19, the scratch depth of the side of the hole 83 formed by the cutting tool 100 of samples 2 to 7 is smaller than that of the hole 83 formed by the cutting tool 100 of sample 1. From this, it was confirmed that the cutting insert 100 of each of the

embodiments

1 and 2 can improve the quality of the hole. In the case of the cutting tool 100 of sample 4, the scratch depth of the side face of the hole was the smallest.

The embodiments and examples disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated not by the above-described embodiments and examples but by the scope of the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

Description of the reference numerals

1 top surface, 2 bottom surface, 3 outer peripheral surface, 4 inner peripheral surface, 5 through hole, 6 cutting edge, 7 chip breaker, 10 st line segment 1, 11 st land surface, 12 st inclined surface, 20 nd line segment 2, 21 nd land surface 2, 22 nd inclined surface 2, 30 rd line segment 3, 31 rd land surface 3, 32 rd inclined surface 3, 40 th line segment 4, 41 th land surface 4, 42 th inclined surface 4, 50 flat portion, 51 st curved portion 1, 52 nd curved portion 2, 53 rd curved portion 3, 54 th curved portion 4, 60 body portion, 61 front end surface 62 outer peripheral side surface, 63 chip discharge groove, 64 fitting portion, 65 rear end surface, 71 outer peripheral side cutting tool placing groove, 72 center side cutting tool placing groove, 73 mounting screw, 80 workpiece, 81 center cutting edge cutting region 82 peripheral edge cutting region, 83 hole, 84 chip, 91 st intersection, 92 nd intersection, 93 st peripheral point, 94 nd peripheral point, 95 imaginary intersection, 100 rotary cutting tool (cutting tool), 200 rotary cutting tool, A1 st tool diameter, A2 center edge share, A3 distance, B rotation axis, D1 st distance, D2 nd distance, L1 st straight line, L2 nd straight line, L3 rd straight line, L4 th straight line, R1 st radius of curvature, R2 nd radius of curvature, R3 rd radius of curvature, R4 th radius of curvature, W1, W11 th cutting edge width, W2, W12 th cutting edge width, W3, W13 th cutting edge width, W4, W14 th cutting edge width.

Claims

1. A cutting tool for a rotary cutting tool, comprising:

a top surface;

a bottom surface opposite the top surface; and

an outer peripheral surface contiguous with each of the top surface and the bottom surface,

wherein a ridge between the top surface and the outer peripheral surface forms a cutting edge,

the cutting edge includes:

the 1 st line segment is a segment of a line,

a2 nd line segment opposite to the 1 st line segment,

a3 rd line segment inclined with respect to each of the 1 st line segment and the 2 nd line segment,

a 4 th line segment opposite the 3 rd line segment,

a1 st bend connecting the 1 st line segment and the 3 rd line segment,

a2 nd bend connecting the 2 nd line segment and the 4 th line segment,

a3 rd bend connecting the 2 nd line segment and the 3 rd line segment, an

A 4 th bend connecting the 1 st line segment and the 4 th line segment,

an angle formed between a straight line along the 1 st line segment and a straight line along the 3 rd line segment is an acute angle,

an angle formed between a straight line along the 2 nd line segment and a straight line along the 4 th line segment is an acute angle,

an angle formed between the straight line along the 2 nd line segment and the straight line along the 3 rd line segment is an obtuse angle,

an angle formed between the straight line along the 1 st line segment and the straight line along the 4 th line segment is an obtuse angle,

a radius of curvature of each of the 3 rd curved portion and the 4 th curved portion is greater than a radius of curvature of the 1 st curved portion and greater than a radius of curvature of the 2 nd curved portion, and

a distance between the top surface and the bottom surface is equal to a distance between the cutting edge and the bottom surface or shorter than the distance between the cutting edge and the bottom surface in a direction perpendicular to the bottom surface.

2. The cutting insert for a rotary cutting tool according to claim 1, wherein the distance between the top surface and the bottom surface is equal to the distance between the cutting edge and the bottom surface in the direction perpendicular to the bottom surface.

3. The cutting tool for a rotary cutting tool according to claim 1,

the top surface has a flat portion spaced from the cutting edge, and

the flat portion is located between the cutting edge and the bottom surface in the direction perpendicular to the bottom surface.

4. A cutting insert for a rotary cutting tool according to any one of claims 1 to 3, wherein the top face comprises:

a1 st land surface continuous with the 1 st line segment,

a2 nd land surface contiguous with the 2 nd line segment,

a3 rd land surface continuous with the 3 rd line segment, an

A 4 th land surface continuous with the 4 th line segment and

each of a width of the 3 rd land surface in a direction perpendicular to the 3 rd line segment and a width of the 4 th land surface in a direction perpendicular to the 4 th line segment is larger than a width of the 1 st land surface in a direction perpendicular to the 1 st line segment and larger than a width of the 2 nd land surface in a direction perpendicular to the 2 nd line segment.

5. The cutting insert for a rotary cutting tool according to any one of claims 1 to 4, wherein each of the radius of curvature of the 3 rd curved portion and the radius of curvature of the 4 th curved portion is 2 times or more and 5 times or less of the radius of curvature of the 1 st curved portion, and 2 times or more and 5 times or less of the radius of curvature of the 2 nd curved portion.

6. The cutting tool for a rotary cutting tool according to claim 1,

said distance between said top surface and said bottom surface being equal to said distance between said cutting edge and said bottom surface in said direction perpendicular to said bottom surface,

the top surface includes:

a1 st land surface continuous with the 1 st line segment,

a2 nd land surface contiguous with the 2 nd line segment,

a3 rd land surface continuous with the 3 rd line segment, an

A 4 th land surface continuous with the 4 th line segment,

each of a width of the 3 rd land surface in a direction perpendicular to the 3 rd line segment and a width of the 4 th land surface in a direction perpendicular to the 4 th line segment is larger than a width of the 1 st land surface in a direction perpendicular to the 1 st line segment and larger than a width of the 2 nd land surface in a direction perpendicular to the 2 nd line segment, and

each of the radius of curvature of the 3 rd curved portion and the radius of curvature of the 4 th curved portion is 2 times or more and 5 times or less of the radius of curvature of the 1 st curved portion, and 2 times or more and 5 times or less of the radius of curvature of the 2 nd curved portion.

7. The cutting tool for a rotary cutting tool according to claim 1,

the top surface has a flat portion spaced from the cutting edge,

the flat portion is located between the cutting edge and the bottom surface in the direction perpendicular to the bottom surface,

the top surface includes:

a1 st land surface continuous with the 1 st line segment,

a2 nd land surface contiguous with the 2 nd line segment,

a3 rd land surface continuous with the 3 rd line segment, an

A 4 th land surface continuous with the 4 th line segment,

8. A rotary cutting tool comprising:

a cutting insert for a rotary cutting tool according to any one of claims 1 to 7; and

and a body portion that holds the cutting insert for a rotary cutting tool.